It is well known to dehydrogenate alkanes in the presence of a dehydrogenation catalyst comprising a Group VIII metal catalyst supported on a highly calcined catalyst support such as alumina, silica or a Group II metal aluminate spinel. In a particular process which causes minimal isomerization of product olefin or olefins, a mixed feed containing alkane and a diluent such as steam or nitrogen is contacted, in the absence of oxygen, with the dehydrogenation catalyst. In this process a plurality of parallel arranged catalyst-filled tubes, which are mounted in a furnace, are utilized to contact the feed and the catalyst under dehydrogenating conditions. Due to the endothermic nature of the dehydrogenation reaction the catalyst is rapidly cooled on contact with the feed. As the reaction proceeds carbon deposits on the catalyst necessitate regenerating the catalyst periodically.
In order to regenerate the catalyst without interruption of the furnace operation, alkane feed flow to a single tube or a group of the tubes is periodically turned off in conjunction with admitting a reactivation medium comprising a free oxygen-containing gas and steam which is supplied to the single tube or group of tubes being regenerated. Upon completion of a regeneration period for one tube or a group of tubes, where carbonaceous deposits on the catalyst are substantially burned off, alkane flow is restarted to the regenerated tubes and another tube or group of tubes is selected for regeneration. In this furnace design the effluent from all tubes is combined so that the oxygen-containing effluent from the tube or tubes being regenerated is mixed in a single gas transfer conduit with the product gas from the product gas-producing tubes.
Although the above described process has the advantage of continuous operation, it experiences the objectionable feature of oxygen-containing regeneration gas entering the hydrocarbon product stream. Under some dehydrogenation conditions the oxygen entering the hydrocarbon product stream can react with the hydrogen or hydrocarbons in the product stream. Under typical dehydrgenation conditions, however, the oxygen can accumulate in various downstream vessels causing potential explosive conditions in the downstream equipment.
Accordingly, it is an object of this invention to improve safety in operating a dehydrogenation process.
A further object of this invention is to increase the safety of a petroleum refining process and the method employed therein.
Another object of this invention is to provide a method for oxygen removal in a catalyst regeneration stage of a dehydrogenation process.